Degree Of Acute Cellular Rejection Research Articles

Induction Versus Maintenance Immunosuppression After Intestinal Transplant: Determining Which Treatment Most Impacts Long-Term Patient And Graft Survival.

Immunosuppressive strategies for intestinal transplant have changed over time. However, specific intestinal transplant-oriented protocols and reports on long-term maintenance regimens are scarce. Our objective was to evaluate the impact of 2 different initial immunosuppressive protocols based on thymoglobulin (group A) and basiliximab (anti-interleukin 2 antibody) (group B) and of changes to maintenance immunosuppression over long-term follow-up in intestinal transplant recipients. We performed a retrospective analysis of a prospectively established protocol for intestinal transplant immunosuppression, conducted between May 2006 and December 2020. We analyzed 51 intestinal transplant recipients, with 6 patients excluded because of early death or graft loss. Acute cellular rejection frequency and grade, number of acute cellular rejection episodes, time to the first acute cellular rejection episode, response to treatment, number of patients who progressed to chronic allograft rejection, kidney function, infections, incidence of posttransplant lymphoproliferative disorder and graft-versus-host disease, and patient and graft survival were analyzed. In the study groups, there were 87 acute cellular rejection episodes in 45 patients (33 in group A and 54 in group B). We found degree of acute cellular rejection to be mild in 45 patients, moderate in 18, and severe in 24 (not significant between groups). Our comparison of induction therapy (thymoglobulin [group A] vs interleukin 2 antibody [group B]) did not show any statistical difference during clinical followup. Long-term review showed that all patients were on tacrolimus. Five-year patient and graft survival rates were 62% and 45% for group A and 54% and 46% for group B, respectively (not significant). Long-term patient and graft outcomes reflected the use of an individualized follow-up with adjustments and changes in immunosuppressive medications according to the patient's clinical course and complications rather than based on the induction immunosuppressive protocol used.

The long term prognostic value of peak left atrial strain in cardiac transplant patients

Abstract Funding Acknowledgements Type of funding sources: None. Background Left atrial (LA) dysfunction is associated with poorer outcomes in many disease processes. Left atrial strain (LAS) is a novel two-dimensional (2D) quantitative analysis of LA function. Cardiac transplantation directly involves the LA during implantation of the donor heart. Traditional echocardiographic indices after transplantation have demonstrated value in correlating with acute cellular rejection (ACR), morbidity and mortality over short- and long-term follow-up. The prognostic value of LA strain has not been previously investigated in this cohort. Purpose We hypothesized that incrementally impaired LA strain in post cardiac transplant patients with varying degrees of ACR may be prognostic of poorer outcomes on long term follow-up. Methods 87 Heart transplant patients, assessed between 2009 and 2015, underwent transthoracic echocardiography and endomyocardial biopsy. 2D strain analysis on the LV and LA were performed along with traditional echocardiographic parameters. Patients were grouped according to peak LAS (PALS) tertiles and rejection burden history was assessed and grouped according to ACR burden at a median of 12 (±5.4) months post transplantation. The primary endpoint was all-cause mortality at follow-up. Results 12 patients met the primary endpoint over a median follow-up of 66 ± 51 months. The mean LA PALS was significantly different across the tertiles (lowest tertile 12.29 ± 2.5% vs middle tertile 17.89 ± 1.1% vs highest tertile 24.54 ± 4.2%; p <0.0001). LA strain dispersion was also significantly different between the tertiles (61.03 ± 25.8ms vs 41.8 ± 15.8ms vs 44.8 ± 18.8ms; p <0.001). All other clinical and echocardiographic parameters were non-significant between the tertiles however, there was a trend towards a lower PALS in the higher rejection burden group. Kaplan Meier curves demonstrated that survival over follow-up was significantly worse in the lower tertile LA PALS group compared to the highest tertiles LA PALS group (Log-rank test = p < 0.0001). The lowest LA PALS tertile had a significantly higher risk of reaching the primary endpoint compared with patients in the highest LA PALS tertile (hazard ratio [HR] 9.802; 95% CI 1.832-52.45; p <0.008). Higher LA PALS and LV GLS (LA PALS HR 0.610 95% CI 0.401-0.926; p 0.02; LV GLS HR 0.638 95% CI 0.418-0.972; p 0.037) were significantly associated with a reduction in reaching the primary endpoint in a multi-variate regression model including clinically relevant traditional and strain-based echocardiographic parameters. Conclusions Lower LA PALS is significantly associated with poorer long-term outcomes in cardiac transplant patients with ACR. Non-invasive LA PALS may be a useful predictor of long-term outcome in patients post cardiac transplantation. Abstract Figure. Survival curves for LA PALS tertiles

QUILTY LESION FOXP3+ AND TGF-BETA+ REGULATORY T-CELLS ARE ASSOCIATED WITH ACCEPTANCE OF HEART ALLOGRAFTS

To evaluate the cellular composition of Quilty lesions in heart transplant biopsies and their association with acceptance or rejection of cardiac allografts. In this study we included a cohort of cardiac transplant biopsies with Quilty lesions for which a final diagnosis had already been rendered for treatment purposes. Serial sections from 42 specimens were stained immunohistochemically for CD4, CD8, FoxP3 (as surrogate marker of innate regulatory T cells) and TGF-beta-1 (as surrogate marker of adaptive regulatory immune cells). The relative abundance of cells positive for each of these four markers was evaluated both in the Quilty lesion itself and in the uninvolved, surrounding myocardium using semi-quantitative methods. Correlations were then made, using chi-square and Pearson analysis, between these measures and allograft acceptance. FoxP3+ (OR 1.33, p<0.05) and TGF-beta+ cells (OR 1.4) in the quilty lesions are associated with higher allograft acceptance. Of note, no FoxP3+ cells were seen in myocardium. However, the presence of CD8+ cells in the myocardium is associated with greater degrees of both acute cellular (p<0.02) and antibody-mediated transplant rejection (p<0.04). High numbers of CD4+ cells in the myocardium are also associated with a greater degree of acute cellular rejection (p<0.04). However, the presence of either CD4+ or CD8+ T-cells in Quilty lesions are not associated with rejection. Interestingly, greater numbers of TGF-beta-positive cells in the myocardium are associated with a greater degree of antibody-mediated rejection. Quilty lesions previously have been associated with mild to moderate acute cellular rejection, but their precise function remains unclear: it has yet to be determined whether they might participate in immune-mediated tissue destruction or may represent an immune-mediated tissue salvage mechanism. In this study, both FoxP3+ innate and TGF-beta+ adaptive regulatory cells are associated with increased allograft acceptance in biopsies when localize? in quilty lesions. Myocardial effector CD4+ and CD8+ T-cells are associated with increased rejection. However, their presence in quilty lesions has no effect in rejection or acceptance or the transplant. Therefore, quilty lesions may rather represent intragraft tertiary lymphoid tissue to prevent allograft rejection, and assist in acceptance of the organ transplant. Drs. George and Anne Race Distinguished Professor of Pathology Endowment Fund (Dr. Jose Torrealba).

Polyfunctional CD8+ T Cells are Associated with Biopsy Proven Acute Cellular Rejection in Pediatric Heart Transplant Patients

Polyfunctional T cells (PTC) have the ability to secrete ≥2 cytokines per cell when stimulated and increased presence of PTC is associated with favorable outcomes in patients undergoing chimeric antigen receptor (CAR) T cell therapy for cancer. In pediatric heart transplant recipients (PHT), the development of PTC may represent increased exposure to donor specific antigens with the potential to induce greater allograft damage through elevated cytokine production; however, the ability of circulating PTC to predict acute cellular rejection (ACR) in PHT is unknown. The goal of this pilot study was to determine the frequency of circulating PTC and secreted cytokine profiles of T lymphocytes in PHT with varying degrees of ACR, with the hypothesis that an elevation in circulating PTC is associated with ACR. Peripheral blood mononuclear cells were collected from PHT concurrently with clinically indicated cardiac biopsy. Single-cell expression profiles of 32 cytokines (Isoplexis Isocode Chip) were quantified in CD4+ and CD8+ T cells from each patient. Samples were stratified by ISHLT biopsy grade for ACR. The polyfunctional strength index (PSI) was calculated as the %PTC multiplied by the intensities of each secreted cytokine. PSI of CD8+ T cells in PHT with ACR 1R (n=4) and 2R (n=2) was increased compared to ACR 0 (n=3; Figure 1). PSI in CD4+ T cells in PHT with ACR was also increased, but less than in CD8+ T cells. Cytokines that drove an increased PSI were granzyme B, macrophage inflammatory protein (MIP)-1a, MIP-1b and sCD137 in CD8+ T cells and MIP-1a, MIP-1b and tumor necrosis factor (TNF)-α in CD4+ T cells. Correspondingly, stimulated cytokine production (CD8+ > CD4+) was increased in PHT with ACR vs no ACR. PHT with ACR had distinct circulating T lymphocyte profiles, specifically with increased polyfunctionality of circulating CD8+ T cells. Quantification of CD8+ PTC may represent a novel biomarker of ACR in PHT and warrants further investigation.

Peripheral Blood Eosinophil Count as a Marker of Pulmonary Allograft Rejection

Purpose Non-invasive methods for early diagnosis of acute cellular rejection (ACR) are needed. Previous studies of other solid organ transplanted recipients have shown a relationship between the eosinophil count in peripheral blood (EOSp) and the presence of ACR. However, the relationship between this biomarker and ACR in lung transplant patients remains unclear.Objective: To asses the relationship between EOSp and the presence of allograft rejection in lung transplant recipients. Methods A retrospective clinical review of 363 transbronchial biopsies (BTB) performed in 194 lung transplant patients between 2014 and 2018. We analyzed: age, date of transplant, the presence and degree of ACR, and the simultaneous absolute number of EOSp. BTB indications were classified as: 1. Protocol BTB in the first month after transplant and after ACR treatment. 2. Decrease of lung function. 3. Other indications The relationship between the EOSp count and ACR was analyzed by the Chi-square test . We calculated the sensitivity, specificity of the EOSp count to diagnose ACR. The precision of the EOS count to predict ACR was analyzed using a receiver operating characteristic ROC curve. Results BTB showed ACR in 117 of 363 cases (32.2%). The most frequent ACR degree was A2 (53%). The EOSp count in patients with ACR was higher than non-ACR patients (197 vs. 92.7; p 197 EOSp was 91% and the area under the ROC curve was 0.724 with 95% confidence interval (CI) 0.636-0.813. Conclusion The monitoring of the EOSp count can be useful to increase the diagnostic yield for ACR of BTB performed by protocol or lung function deterioration.

Evaluation of the Graft Mechanical Function Using Speckle-Tracking Echocardiography During the First Year After Orthotropic Heart Transplantation.

BackgroundRecent advances in ultrasound strain imaging facilitate more precise monitoring of subtle myocardial changes and thus may allow for more appropriate assessment of myocardium after orthotopic heart transplantation (OHT). This study aimed to explore longitudinal left ventricular (LV) and right ventricular (RV) function by speckle-tracking echocardiography (STE) during a 12-month follow-up period in relation to acute cellular rejection (ACR) degree ≥2R and the response to intense immunosuppressive therapy with intravenous steroids.Material/MethodsForty-five adult heart transplant recipients were prospectively assessed at a single center from January 2016 until June 2017. Echocardiography was performed serially at baseline and together with routine biopsies at 2 weeks and 1, 2, 3, 6, 9, and 12 months after OHT. Changes in graft function were evaluated using STE before and during ACR and in the resolving period of ACR.ResultsA total of 220 pairs of biopsy specimens and strain recordings were analyzed. Moderate ACR was seen in 30 biopsies (13.6%). In the serial assessment, longitudinal strain parameters of the LV (global and 4-, 2-, 3-chamber longitudinal strain) and RV (global and free wall longitudinal strain) were decreased at baseline and improved significantly (P<0.001) within 12 months after OHT. The degree of improvement was not influenced by ACR. There were no significant differences in circumferential, radial, or longitudinal strain rate, or mechanical dyssynchrony. Reduced LV and RV longitudinal strain was related to ACR degree 2R and increased significantly (P<0.0005) during 3 days of intravenous methylprednisolone therapy.ConclusionsUsing the STE technique, we have documented an acute improvement in mechanical myocardial function following ACR steroid therapy and a progressive recovery of LV and RV longitudinal function during the first year after OHT.

Paneth and Intestinal Stem Cells are Differentially Affected during Worsening of Acute Cellular Rejection in Small Bowel Transplantation compared to Intestinal Ischemia Reperfusion Injury and Graft versus Host Disease

Instituto de Estudios Inmunológicos y Fisiopatológicos, UNLP-CONICET, La Plata, Argentina. Introduction Acute cellular rejection (ACR) is one of the leading causes of graft loss after small bowel transplantation (SBTx). Although crypt epithelial cell apoptosis is used as histopathological criteria for ACR diagnosis, it is not clear which of epithelial lineages are the target of ACR. It was shown that the number of enteroendocrine progenitor cells in intestinal crypts was reduced during mild ACR, however, no results on other cell types of the crypt have been depicted so far. The aim of our work was to elucidate integrity and functionality of Paneth and stem cells during different degrees of ACR, in comparison with other clinical conditions such as graft vs. host disease (GVHD) and ischemia reperfusion injury (IRI). Material and Methods 44 patients of SBTx and controls treated in our center between 2006 and 2016 were included in the study. Rejection diagnosis was established by an experienced pathologist according to the recommendations of the pathology workshop of the VIII Small Bowel Transplantation Symposium. We compared small biopsies from SBTx patients with no, mild, moderate or severe ACR by immunohistochemistry and quantitative PCR (n=10 per group as average) for different cell markers (Lgr5, lysozyme, defensin5, IL22R, Ki67). Other conditions such as different degree of intestinal GVHD and IRI were included as separate groups. Comparisons among groups of data were performed with the Kruskal-Wallis test and the Dunn`s post-test when more than two groups were analyzed, whereas the Mann-Whitney U test was chosen to compare data from two groups. Results and Discussion Using differential immunofluorescence counting of different markers we observed that numbers of Paneth and stem cells remain constant in all ACR groups, whereas the transit-amplifying zone is the region that concentrates most of the apoptotic bodies during ACR (p<0.05). We detected unchanged level of antimicrobial peptides in Paneth cells and similar numbers of Ki-67+IL-22R+ stem cells revealing cell functionality in moderate ACR samples. Oppositely, in GVHD of moderate to severe, as well as IRI, Paneth cell number and markers were diminished (p<0.05), indicating differential mechanism that operate to trigger epithelial cell apoptosis in different situations. Conclusion Paneth and stem cells are not primary target cells during ACR. IL-22R + Ki-67+ stem cells might be an interesting target cell population for protection and regeneration of the epithelial monolayer during/after a severe ACR in ITx patients.

Paneth and intestinal stem cells preserve their functional integrity during worsening of acute cellular rejection in small bowel transplantation.

Graft survival after small bowel transplantation remains impaired due to acute cellular rejection (ACR), the leading cause of graft loss. Although it was shown that the number of enteroendocrine progenitor cells in intestinal crypts was reduced during mild ACR, no results of Paneth and intestinal stem cells localized at the crypt bottom have been shown so far. Therefore, we wanted to elucidate integrity and functionality of the Paneth and stem cells during different degrees of ACR, and to assess whether these cells are the primary targets of the rejection process. We compared biopsies from ITx patients with no, mild, or moderate ACR by immunohistochemistry and quantitative PCR. Our results show that numbers of Paneth and stem cells remain constant in all study groups, whereas the transit-amplifying zone is the most impaired zone during ACR. We detected an unchanged level of antimicrobial peptides in Paneth cells and similar numbers of Ki-67+ IL-22R+ stem cells revealing cell functionality in moderate ACR samples. We conclude that Paneth and stem cells are not primary target cells during ACR. IL-22R+ Ki-67+ stem cells might be an interesting target cell population for protection and regeneration of the epithelial monolayer during/after a severe ACR in ITx patients.

Usefulness of Two-Dimensional Strain Parameters toDiagnose Acute Rejection after Heart Transplantation.

Acute cellular rejection (ACR) is still a relevant complication after orthotopic heart transplantation. The diagnosis of ACR is based on endomyocardial biopsy (EMB). Recent advances in two-dimensional strain imaging may allow early noninvasive detection of ACR. The objective of this study was to analyze the usefulness of conventional and new echocardiographic parameters to exclude ACR after orthotopic heart transplantation. Thirty-four consecutive adult heart transplant recipients admitted to a single center between January 2010 and December 2012 for orthotopic heart transplantation were prospectively included. A total of 235 pairs of EMB and echocardiographic examination were performed. A median of seven studies per patient (interquartile range, six to eight studies per patient) were performed during the first year of follow-up. Classic echocardiographic parameters; speckle-tracking-derived left ventricular (LV) longitudinal, radial, and circumferential strain; and global and free wall right ventricular (RV) longitudinal strain were analyzed. ACR was detected in 26.4% of EMB samples (n=62); 5.1% (n=12) required specific treatment (ACR degree≥2R). Lower absolute values of global LV longitudinal strain and free wall RV longitudinal strain were present in patients with ACR degree≥2R compared with those without ACR (13.7±2.7% vs 17.8±3.4% and 16.6±3.6% vs 23.3±5.2%, respectively). An average LV longitudinal strain < 15.5% had 85.7% sensitivity, 81.4% specificity, 98.8% negative predictive value, 25.0% positive predictive value, and 81.7% accuracy for the presence of ACR degree≥2R. Free wall RV longitudinal strain < 17% had 85.7% sensitivity, 91.1% specificity, 98.8% negative predictive value, 42.9% positive predictive value, and 90.7% accuracy for ACR degree≥2R. Both variables were normal in 106 echocardiograms (57.6%); none of these patients presented with ACR degree≥2R. The combination of two new echocardiographic measures, global LV and RV free wall longitudinal strain, may be able to identify a group of heart transplant patients who are unlikely to have ACR. If these findings are confirmed independently, it may be possible to use LV and RV strain measures as reliable tools to exclude ACR and to reduce the burden of repeated EMB.

The number of regulatory T cells in transbronchial lung allograft biopsies is related to FoxP3 mRNA levels in bronchoalveolar lavage fluid and to the degree of acute cellular rejection

BackgroundThe transcription factor Forkhead Box P3 (FoxP3) is a marker of regulatory T cells (Tregs) — a subset of T cells known to suppress a wide range of immune responses. These cells are considered to be pivotal for the induction of tolerance to donor antigens in human allografts. We aimed to correlate the number of lymphocytes expressing FoxP3 in transbronchial biopsies from lung allografts with the FoxP3 expression in bronchoalveolar lavage fluid (BALF). In addition, we aimed to correlate the number of FoxP3+ cells in transbronchial biopsies with the degree of acute cellular rejection in lung allografts. Materials and methodsThe expression of FoxP3 was evaluated using immunohistochemical staining in 40 lung allograft biopsies obtained from 23 patients. The number of Tregs was related to the FoxP3 mRNA levels as determined using qRT-PCR in corresponding BALF samples from the same patients. Furthermore, the number of Tregs was related to the degree of acute allograft rejection (according to ISHLT criteria, A0–A4). ResultsRegression analysis showed a significant concordance between the number of Tregs in lung tissue and the level of FoxP3 mRNA relative to glyceraldehyde 3-phosphate dehydrogenase (GAPDH) mRNA levels in BALF (n=40, p=0.0001). In addition, we found a significant increase in the number of Tregs during acute allograft rejections of grades A2 and higher (median: 32.6Tregs/mm2) when compared to those of grades A1 and A0 (median: 4.9Tregs/mm2) (p=0.0002). Discussion and conclusionThe association between the distribution of Tregs in transbronchial biopsies and the level of FoxP3 mRNA in BALF indicates that assessment of FoxP3 mRNA in BALF is a reliable non-invasive method for evaluating the number of Tregs in lung tissue. Furthermore, the association between the number of Tregs in lung tissue and the degree of acute cellular rejection shows that Tregs are recruited to the site of inflammation and may be involved in the regulation of acute rejection. Thus, Tregs may play a role in the cellular processes that affect lung allograft outcome.

Basiliximab as therapy for acute rejection after liver transplantation for hepatitis C virus cirrhosis

Steroid bolus therapy for acute rejection after liver transplantation for hepatitis C virus (HCV) cirrhosis often results in graft loss due to adverse effects. The efficacy and safety of basiliximab for the treatment of acute cellular rejection (ACR) in adult liver transplantation has not been adequately evaluated. Three patients received basiliximab as rescue therapy for acute rejection. The outcome and biochemical parameters were recorded before and after treatment with basiliximab. These results were compared to 11 patients who received steroid therapy for ACR. The median time from transplantation to the development of ACR was 19 days (range, 9-49 days). The degree of ACR was mild or moderate. Resolution of rejection was obtained in all patients and the median time from the onset to resolution of ACR was 16 days (range, 6-41 days). A steroid resistant reaction occurred in 2 of 11 patients and OKT3 was used, and the rejection eventually resolved in all patients. Five patients died within 2 to 22 months after transplantation and four of them died from graft failure. In the basiliximab group, there were no significant immediate adverse effects. One patient died from pneumonia 8 months after transplantation. Basiliximab can be safely used as rescue therapy for ACR without significant adverse effects in patients who underwent liver transplantation for HCV cirrhosis.

Foxp3 Staining in BK Virus Allograft Nephropathy and Comparison With Acute Cellular Rejection

Background Foxp3 +CD4 +CD25 + regulatory T cells are involved in maintaining immunologic self-tolerance. These cells have been investigated in acute cellular rejection (ACR) of renal allografts. In this retrospective pathological study, we evaluated Foxp3 + immunostaining in BK virus nephropathy (BKVN). In some circumstances, BKVN may be difficult to distinguish histologically from ACR. Methods Sequential sections were made of 30 allograft core biopsies and stained for hematorylin and eosin (H&E), C4d, cytomegalovirus (all negative), SV40, CD3, CD20, and Foxp3. Twelve biopsies were from diagnosed BKVN cases, 12 were from diagnosed ACR cases, and six showed neither BKVN nor ACR (controls). The 100× field of maximum cellular inflammation was located and marked on the H&E stain. The same area on the CD3, CD20, and Foxp3 slides was marked. Staining lymphocytes were counted under 400× magnification. Degree of BKVN was assessed according to the Drachenberg scale; degree of ACR was assessed by the Banff criteria. Results The range of Foxp3 + staining (cells/mm 2) was much larger in BKVN (0–270) compared to ACR (0–35). The mean difference did not reach statistical significance owing to a large degree of overlap between the two groups. In BKVN, the Foxp3 + infiltrate correlated with the degree of CD3 + infiltrate ( P = .012), and median Foxp3 + infiltrate increased with Drachenberg grade of BKVN. CD3 + cell levels were not significantly different in BKVN versus ACR. Conclusions BKVN cases with high levels of Foxp3 + graft infiltrates may be manifesting an immune response different from that of ACR. Positive Foxp3 correlation with Drachenberg grade suggests a down-regulatory response.

Dynamics of Human Regulatory T Cells in Lung Lavages of Lung Transplant Recipients

Despite advances in the field of lung transplantation, the median survival after lung transplant remains below 5 years. Early rejection is a risk factor for the development of chronic rejection. In animal models of transplant tolerance, regulatory T cells (Tregs) can prevent the establishment of rejection. This study was designed to explore the dynamics of Tregs focally and systemically in lung transplant recipients. Sequential surveillance bronchoscopy results were available in 51 patients with at least four sequential samples recovered from each patient at defined times posttransplant. In 36 individuals, a complete year of follow-up data for BAL was analyzed. In 33 of these individuals had a complete year of follow-up data for peripheral blood monocyte cell specimens were also analyzed. Lung lavage cells were recovered from each bronchoscopy and corresponding blood draw and subjected to polychromatic flow cytometry. The percentage of CD4 lymphocytes, which expressed the intracellular transcription factor FoxP3 was recorded at each point. At each time point, lung biopsy specimens were scored for rejection. Lung Treg frequency was significantly more variable than blood Treg frequency. Treg frequency in the lung was increased in the aftermath of acute rejection. In contrast, lung Treg frequency declined sequentially in patients demonstrating continued quiescence. Mean BAL Treg level integrated over the first transplant year correlated inversely with the degree of acute cellular rejection. In contrast, blood Treg levels demonstrated no correlation with lung pathology. Lung Tregs increase in the setting of acute cellular rejection, whereas declining levels of BAL Tregs correlates with immunologic quiescence.

Correlation of Motility and Neuronal Integrity with a Focus on the Grade of Intestinal Allograft Rejection

Intestinal graft motility after small bowel transplantation (SBT) is poorly characterized. The aim of this study was to compare motor patterns with myenteric neuronal cell population as a parameter of graft viability at various degrees of acute cellular rejection (ACR). Three grades of ACR were achieved in orthotopic allografts. Syngeneic transplants and allografts with immunosuppression served as controls. Motor activities were recorded using strain gauge force transducers and analyzed visually. Quantifications of myenteric neurons in whole mounts of intestinal grafts were used to evaluate neuronal population. A typical migrating motor complex (MMC) was found in syngeneic and allogenic transplants with immunosuppression. A high prevalence of discrete clustered contractions (DCC) and nonpropagating contractions (NPC) without MMC was seen in moderately and severely rejected allografts. Neuronal cell loss in the allografts, which could be one of the causes of motor dysfunction, was noted in moderate rejection (19.3%) and progressed until severe rejection (60.1%). Monitoring motility patterns in SBT could be an effective tool for assessing intestinal rejection. Allograft dysmotility, such as absence of MMC and high prevalence of DCC or NPC, could be useful markers of progression of acute rejection and help guide treatment decisions.

Pathology of liver transplantation

Summary Liver transplantation has been increasingly used over the past four decades as an effective treatment for end-stage liver disease. Although the demand exceeds the supply of cadaveric organs, the donor pool has expanded with the increasing use of split-liver grafts, non-heart-beating donor livers and living-related donors. Histopathologists play a role in the pre-transplant and post-transplant period; their input is crucial in both identifying and monitoring post-transplant complications. The degree of acute cellular rejection is best assessed histologically, and biopsy interpretation informs changes to the immunosuppressive regimen. Chronic rejection is characterised by progressive ductopenia; a number of lesions have been identified that predict the likelihood of progression to chronic rejection. Other post-transplant complications readily assessed on liver core biopsies include vascular and biliary complications, infectious, recurrent and de novo disease. De novo hepatitis with ‘autoimmune' features is described as is idiopathic chronic hepatitis, but the relationship of these lesions to alloimmune pathways remains uncertain. Although liver transplantation is generally performed in specialist centres, an increasing number of histopathologists working in non-specialist units are being exposed to post-transplant biopsies and need to be aware of the spectrum of changes that can occur.

Heme-oxygenase-1 expression correlates with severity of acute cellular rejection in lung transplantation.

Heme-oxygenase-1 (HO-1) has been shown to play an important role in oxidative stress, and recent studies indicate that it is a graft survival protein in cardiac and liver transplant models. Our laboratory previously found HO-1 to be increased in human lung allografts with acute cellular rejection (ACR) and in active obliterative bronchiolitis. To better understand the role of HO-1 in ACR we studied the relationship between HO-1 expression and ACR in a rodent model of lung transplantation. Orthotopic left lung transplantation was performed from Lewis (donor) to Sprague-Dawley (recipient) rats, and ACR (Grade A0 to A4) was evaluated at days 3, 5, and 7. HO-1 expression was assessed by immunohistochemistry and Western analysis, and compared with the degree of ACR. Myeloperoxidase staining was evaluated as an indirect measure of oxidant stress. Donors and recipients were also treated with either an inhibitor of HO activity, tin protoporphyrin or an inducer, cobalt protoporphyrin, and the severity of ACR was compared with that in untreated allografts. HO-1 expression was elevated in transplanted versus native lungs or isografts, and the degree of elevation was closely correlated with ACR grade (p < 0.001). Similarly, myeloperoxidase expression increased with time and severity of ACR. Administration of the metalloporphyrins, tin protoporphyrin and cobalt protoporphyrin, produced no significant difference in the degree of ACR, but did alter the severity of ischemia-reperfusion injury. Similar to what occurs in human lung transplantation, HO-1 expression is increased in a rodent lung transplant model of ACR and correlates with the severity of rejection. Altering its expression does not appear to affect the degree of ACR.

Serum citrulline and rejection in small bowel transplantation: a preliminary report.

There is no known serum marker for intestinal rejection. Serum concentrations of the amino acid citrulline arise almost exclusively from the intestinal mucosa. We examined the impact of acute cellular rejection (ACR) of intestinal allografts on serum citrulline levels. Citrulline concentrations were assayed in serum samples of healthy volunteers (n=6) and seven patients who underwent small bowel transplants (SBTx). Trends in mean citrulline concentrations versus degree of ACR were assessed by matching posttransplantation citrulline concentrations with patients' grade of ACR at time of serum collection. Rejection was confirmed by biopsy and graded by following standardized criteria. An additional patient had citrulline concentrations determined for 31 sequential specimens 3-60 days posttransplant. Mean citrulline concentrations in controls were significantly higher than posttransplantation samples at any rejection grade. Mean concentrations declined significantly as rejection severity increased. The overall downward trend was statistically significant (P<0.05). In sequential measurements, citrulline levels increased significantly over time with declining severity of rejection. The increase in mean citrulline concentration between posttransplant days 3-16 and 52-60 was significant (P<0.01). Serum citrulline levels decline with increasing grade of ACR and may be a useful serum marker for intestinal rejection.

Measurement of portal venous flow velocity with an implantable miniature Doppler probe in pig liver transplantation.

Portal venous flow (PVF) was serially monitored after pig liver transplantation (LTX) with the use of an implantable, miniature Doppler probe developed in our laboratory. Throughout the study period, the mean PVF in pigs that underwent LTX was significantly greater than that in pigs that were sham operated. For three animals with early graft failure secondary to primary nonfunction and for six that survived longer than 7 days, the mean PVF on postoperative day (POD) 1 was 18.7 +/- 3.8 cm/s and 41.7 +/- 11.2 cm/s, respectively (P < 0.05). For animals with acute cellular rejection (ACR), the mean PVF was 61.3 +/- 9.9 cm/s on POD 7 and 54.3 +/- 6.38 cm/s on POD 14. These values were significantly higher than those for animals without ACR (P < 0.05). Moreover, the increase in PVF correlated well with the degree of ACR. The actual PVF volume was measured by ex vivo perfusion, which showed a clear correlation with the PVF velocity obtained with the implanted, miniature Doppler probe. We feel that the liver graft requires increased PVF volume after transplantation to facilitate functional recovery from damage to hepatocytes due to preservation-reperfusion injury, and that ACR is also associated with an increased PVF. We conclude that monitoring the PVF in the early postoperative period after LTX is useful in the evaluation of graft function, particularly for predicting primary nonfunction and severity of ACR.

Isolated pancreas rejection in combined kidney pancreas tranplantation.

The clinical success of pancreas transplantation is limited by the difficulty in diagnosing rejection. In simultaneous pancreas kidney (SPK) transplantation, the diagnosis of pancreatic rejection is particularly difficult in the absence of clinical evidence of kidney rejection. Moreover, patients receiving only pancreas grafts will not have a concomitantly grafted kidney to serve as a "sentinel" for rejection. Percutaneous pancreas graft biopsy has been reported in a few small series but has not been adopted for broad clinical use. We describe the evaluation of 69 consecutive episodes of suspected isolated pancreas allograft rejection by percutaneous pancreas allograft biopsy. These rejection episodes occurred in 41 patients with bladder-drained pancreas transplants (25 SPK, 14 pancrease after kidney transplants [PAK], amd two pancreas transplant alone [PTA]). The indications for percutaneous pancreas biopsy were a twofold or greater increase in serum amylase or lipase, or a sustained 40% to 50% drop in urine amylase in the setting of no evidence of renal allograft dysfunction in SPK transplants. Biopsies were performed with color-flow Doppler ultrasound localization using an 18-gauge automated biopsy needle. Pancreatic tissue adequate for histologic evaluation was obtained in 61 of 69 cases (88%). There were two cases of intraabdominal bleeding, one of which required surgical intervention; the other resolved spontaneously. Histologic assessment of the biopsies demonstrated varying degrees of acute cellular rejection in 48 of 61 specimens (79%). Twelve specimens (20%) were free of histologic evidence of rejection, and one specimen (2%) showed acute pancreatitis. At the time of suspected rejection mean serum amylase and lipase values were increased 3.6 and 8.3-fold, respectively, and urine amylase was decreased by a mean of 45%. We conclude that the commonly used markers for pancreas allograft rejection are only about 80% specific for acute rejection. Percutaneous pancreas allograft biopsy is safe and allows the avoidance of unnecessary antirejection therapy with its attendant side effects and cost.